mod_watchdog defines programmatic hooks for other modules to
periodically run tasks. These modules can register handlers for
mod_watchdog hooks. Currently, the following modules in the
Apache distribution use this functionality:
- mod_heartbeat
- mod_heartmonitor
- mod_md
- mod_proxy_hcheck
To allow a module to use mod_watchdog functionality,
mod_watchdog itself must be statically linked to the server
core or, if a dynamic module, be loaded before the calling module.